Predictors of respiratory illness in western lowland gorillas

Abstract

Infectious disease is hypothesized to be one of the most important causes of morbidity and mortality in wild great apes. Specific socioecological factors have been shown to influence incidences of respiratory illness and disease prevalence in some primate populations. In this study, we evaluated potential predictors (including age, sex, group size, fruit availability, and rainfall) of respiratory illness across three western lowland gorilla groups in the Republic of Congo. A total of 19,319 observational health assessments were conducted during daily follows of habituated gorillas in the Goualougo and Djéké Triangles over a 4-year study period. We detected 1146 incidences of clinical respiratory signs, which indicated the timing of probable disease outbreaks within and between groups. Overall, we found that males were more likely to exhibit signs than females, and increasing age resulted in a higher likelihood of respiratory signs. Silverback males showed the highest average monthly prevalence of coughs and sneezes (Goualougo: silverback Loya, 9.35 signs/month; Djéké: silverback Buka, 2.65 signs/month; silverback Kingo,1.88 signs/month) in each of their groups. Periods of low fruit availability were associated with an increased likelihood of respiratory signs. The global pandemic has increased awareness about the importance of continuous monitoring and preparedness for infectious disease outbreaks, which are also known to threaten wild ape populations. In addition to the strict implementation of disease prevention protocols at field sites focused on great apes, there is a need for heightened vigilance and systematic monitoring across sites to protect both wildlife and human populations.

Keywords: Conservation; Cough; Ecology; Great apes; Infectious disease; Outbreak; Sneeze; Sociality.

Fig. 1

Focal group members with respiratory signs relative to number of members not displaying signs of respiratory illness by month. The black line indicates potential outbreaks within the groups. Note that simultaneous outbreaks across groups were identified in December 2015 and February 2017

Fig. 2

Probability of the presence of respiratory signs by age for all groups. Ages have been binned. Each circle represents one individual per age category

Fig. 3

Probability of observed respiratory signs (coughing and sneezing) across fruit availability by month for all groups. Fruit availability values have been binned, with each circle representing one individual per fruit availability category